Jewish law prohibits turning lamps on or off for at least approximately a 24 hour period, for example, on the Jewish Sabbath, and on certain Jewish holidays. This period may be as long as 72 hours if the Sabbath precedes or follows certain Jewish festival days. This proscription generally prevents a person from turning a source of current or lamp switch on and off, or varying the current, for example using a dimmer switch to dim or brighten the light. However, blocking and unblocking the light mechanically is generally not proscribed. Using light timers is also not proscribed, and these devices enjoy a significant role in addressing the proscription, however their utility is limited in situations in which one cannot predict when the light is needed to be on and off.
Moving a lamp on the Sabbath is also generally proscribed.
Accordingly, there is a market among Sabbath-observant Jewish people for a lamp in which the light source can be mechanically blocked and unblocked, in the place where it has been left for use on the Sabbath. Such a lamp is particularly in demand in a bedroom so that the room can be darkened at will.
U.S. Patent Publication No. 2003/0026099 describes a lamp comprising a set of partially opaque light enveloping covers for enveloping a light source. A lamp embodying the invention described in this application is currently on the market. The lamp comprises a base configured to sit on a flat horizontal surface, a bulb operatively mounted over the base, a cylindrical light source encasement element, which is partially translucent and partially opaque, and a cover which is opaque, except for an oval aperture which allows the light to be transmitted. The cover is rotatably mounted on the light source encasement for rotation about an axis perpendicular the base. By rotating the cover about its own axis, the user can align oval aperture with the portion of the light source encasement element which is translucent to allow the light to be transmitted through the oval aperture. Perfect alignment of the oval aperture and translucent portion of the underlying light source encasement element will transmit the maximum amount of light in the direction to which the aperture is open whereas partial alignments transmit variable amounts of light. Rotation in at least one direction can causes complete misalignment of the oval aperture with the translucent portion of the light source encasement element to substantially block the light, for example, to darken a room for sleeping. The base and cover are provided with heat dissipating slots that are positioned to avoid transmission of light.
One of the limitations of the above lamp design is that increasingly misaligning the light encasement elements (i.e. to reduce the amount of light) also causes the light to be increasingly directionally transmitted. This limitation can be most disadvantageous when the ideal amount of transmitted light (for example to promote sleep of one individual and continued activity of other individuals) is intended to be shared by family members and the otherwise ideal locations of the respective family members in the room for whom darkness is ideal are not compatible with the direction in which transmission of light from the lamp is blocked.
For example, when bringing the lamp on a trip, if the transmitted light is meant to be substantially reduced to permit a family member (e.g. a child) to sleep while others read by its light, its placement on a night table between two hotel beds or on a breakfast table, diminishes the amount of the light for reading on one side of the table because the light is directionally transmitted via the slot. For example, if the lamp is positioned so that the direction of light transmission benefits both sides of the table equally, the alignment of the slot needs to be adjusted so that more light is transmitted into the room (contrary to what is indicated for sleeping), because this orientation of the lamp is now sub-optimal for both users.
U.S. Patent Publication No. 2005/0213330 describes a lamp adapted for Sabbath observance which comprises an opaque cover configured to be placed over an incandescent bulb. The cover is configured to be placed on (or lifted off) a cover support platform. The cover support platform and the cover together envelop the bulb to block light transmission from the light bulb. The cover must be completely removed and replaced, to alternately reveal and block the light source and therefore cannot be adjusted to vary transmission of light. Furthermore, removal of the cover may cause the cover to become separated and misplaced.